Hundreds of cases where there was no prosecution could be re-examined.

Mr Starmer emphasised that he was not suggesting that the test for whether or not to prosecute should change.

In addition to new guidelines for police and prosecutors in England and Wales, a panel will review cases where alleged perpetrators were not charged and new training will be offered to those dealing with child exploitation cases.

The panel will advise chief constables on whether the case should be reopened, and Mr Starmer says he expects the number of cases to be in the "hundreds not thousands".

'Pattern of behaviour'

But he said after the Jimmy Savile affair there was a sense "the pendulum needs re-positioning again".

A review into allegations against the late DJ and TV presenter said he had carried out more than 200 sexual offences over a 54-year period.

Allegations were reported to police several times while he was alive but no action was taken against him.

Mr Starmer said many victims did not have the confidence to come forward and the standards used for establishing the credibility of someone making an allegation can mean vulnerable victims are not believed.

Analysis

By Danny ShawHome affairs correspondent, BBC News

"A new genre of miscarriages of justice has arisen from the over-enthusiastic pursuit of these allegations". Those were the words of the Home Affairs Committee in 2002 after hundreds of people had been investigated about historical child abuse in children's homes and other institutions.

Many were wrongfully convicted and as a result the justice pendulum swung the other way: police adopted a more sceptical approach and prosecutors were more picky about the cases they took to trial.

Now, after the Savile affair and the emergence of other sex abuse allegations that have lain dormant for years, there's a sense that the pendulum needs re-positioning again.

The difficulty, as Keir Starmer acknowledges, is to set the right balance - so that investigators adopt a less cautious approach to what victims say while testing and questioning their accounts.

Experience suggests it won't be easy: expect a few cases to go wrong before things settle down.

This is because complainants often have characteristics - such as a distrust of authority and alcohol issues - which both make them vulnerable and put their credibility in doubt.

In future, investigators will be expected to test the credibility of an allegation by focusing on the suspect as well as the alleged victim.

"At the moment there is a great deal of focus on whether the victim is telling the truth. We need to look equally carefully at the account the suspect has given - look at the context, the pattern of behaviour and make the necessary links," Mr Starmer said.

The new College of Policing, with the agreement of the Crown Prosecution Service and Association of Chief Police Officers (Acpo), will develop a new strategy to replace the 19 sets of guidelines for investigating child sexual abuse that currently exist.

The CPS has no policy relating specifically to child sexual exploitation, and Mr Starmer believes one "overarching" approach to the investigation and prosecution of sexual offences is needed.

Mr Starmer spoke about the Savile case and the Rochdale grooming case, which led to nine men being jailed last year. It emerged during their trial that the police and social services had missed opportunities to stop the abuse.

'Current atmosphere'

Mark Newby, a solicitor who formed a panel to look at historical child abuse allegations, said he was "gravely concerned" the balance might be shifted too far in favour of the victim.

"We have to be really careful not to create a whole new genre of miscarriage because of the current atmosphere and pandemonium over these cases," he told BBC Radio 4 Today's programme.

"Teachers, social workers, therapists, the police - they all have to come together to try and improve their collective understanding of child sexual abuse and to acknowledge, frankly, how it's much more prevalent than people ever dream of," he told BBC One's Breakfast.

Alan Wardle, head of corporate affairs at children's charity NSPCC, said he hoped the new approach would encourage victims to come forward.

"Making them think they will be taken seriously and that they're not going to be crucified by the whole process as they go through the criminal justice system is really important in helping tackle the scourge of child sexual abuse in this country," he said.

Childline founder Esther Rantzen told the BBC the plans were a "very important first step" but they would not address the problem of "ferocious" cross-examining of children in courtrooms.

"The legal system has been created to frighten adults into telling the truth and what it's been doing for decades is frightening children into silence," she said.

The draft guidelines are expected to be ready in May for a three-month public consultation.